Python program to create a dictionary from a string

In this article, we will learn different methods to convert a string into a dictionary in Python. This is useful when you have string data that represents key-value pairs and need to work with it as a dictionary.

Problem statement ? We are given a string input and need to convert it into a dictionary type.

Here we will discuss three methods to solve this problem, each suitable for different string formats.

Method 1 ? Using eval() Function

The eval() method works when the string syntax already resembles a dictionary format with curly braces, quotes, and colons. This method directly evaluates the string as Python code ?

Example

# String in dictionary format
string = "{'T':1, 'U':2, 'O':4, 'R':5}"

# Using eval() function
dict_string = eval(string)
print("Dictionary:", dict_string)
print("Value of 'T':", dict_string['T'])
print("Type:", type(dict_string))

Dictionary: {'T': 1, 'U': 2, 'O': 4, 'R': 5}
Value of 'T': 1
Type: <class 'dict'>

Note: Use eval() carefully as it can execute arbitrary code and pose security risks with untrusted input.

Method 2 ? Using Generator Expression

For strings with custom delimiters like dashes and commas, we can use generator expressions with split() to parse and create the dictionary ?

Example

# String with custom format
string = "T-3, U-2, O-4, R-5"

# Converting string to dictionary using generator
dict_string = dict((x.strip(), y.strip()) 
                   for x, y in (element.split('-') 
                   for element in string.split(', ')))

print("Dictionary:", dict_string)
print("Value of 'T':", dict_string['T'])
print("All keys:", list(dict_string.keys()))

Dictionary: {'T': '3', 'U': '2', 'O': '4', 'R': '5'}
Value of 'T': 3
All keys: ['T', 'U', 'O', 'R']

Method 3 ? Using json.loads() for JSON Strings

When the string is in JSON format, json.loads() is the safest and most reliable method ?

Example

import json

# JSON formatted string
json_string = '{"name": "Alice", "age": 25, "city": "New York"}'

# Converting JSON string to dictionary
dict_from_json = json.loads(json_string)
print("Dictionary:", dict_from_json)
print("Name:", dict_from_json['name'])
print("Age:", dict_from_json['age'])

Dictionary: {'name': 'Alice', 'age': 25, 'city': 'New York'}
Name: Alice
Age: 25

Comparison

Conclusion

Use json.loads() for JSON-formatted strings, generator expressions for custom delimited formats, and avoid eval() unless you completely trust the input source. Choose the method based on your string format and security requirements.